A correlation of venous blood concentrations and spinal fluid concentrations of Xylocaine and Citanest during peridural analgesia.

Abstract

SUMMARY I. A study of the venous blood concentration of various doses and concentrations of Xylocaine and Citanest with or without the addition of epinephrine which follows the peridural administration of these agents indicate the following: 1 The systemic toxicity of Xylocaine is lower than suggested by some authors. This is indicated by the relatively low venous blood concentration which follows the administration of moderate to large doses. 2 Citanest possesses a lower systemic toxicity than Xylocaine and it is probably more rapidly metabolized. 3 It is not logical to utilize weight in determining the dose of local anesthetic agents to administer peridurally. 4 There is no correlation between blood concentrations of these local anesthetic agents and the blood count or hemoglobin values. 5 It is the total dose rather than the concentration of these anesthetic agents which determines the venous blood levels. 6 Epinephrine 1:200,000 markedly reduces systemic toxicity by decreasing absorption from the peridural space. 7 The maximum concentration of these agents occurs in approximately 20 minutes in the venous blood. II. A study of the spinal fluid concentrations of Xylocaine and Citanest which develop during peridural or spinal anesthesia indicates the following: 1 The concentrations of local anesthetic agents in spinal fluid which follow peridural injection are low and consequently are not believed to be of significance in the production of peridural analgesia. 2 The concentration of local anesthetic agents in spinal fluid remains rather high for considerable periods of time following intrathecal injection. 3 There is no relationship between the segmental levels of analgesia and the concentration of local anesthetic agents in spinal fluid during peridural or spinal anesthesia. 4 Citanest has greater penetration power or diffusion capacity than Xylocaine. 5 Citanest, in comparable doses, produces longer duration of action than Xylocaine whether injected intrathecally or peridurally.